1. Field of the invention
The present invention relates to a photographic processing cassette for the processing of an image-wise exposed photographic silver halide emulsion layer element and to a photographic image-forming apparatus for the convenient processing of photographic film sheets, incorporating such processing cassette such as a microfilm camera or a COM (computer output microfiche) device for the production of microfiches, a phototypesetter, etc.
2. Description of the related art
Micro-images are commonly photographically processed according to one of the following two processes.
The first process is a "dry processing" silver halide system, wherein an image is generated by exposure and thermal development of a light-sensitive layer containing minor amounts of light-sensitive silver halide, an organic silver soap and a reducer. This system has the important advantage of dry processing (no liquids), but it has been shown that the storage conditions of the processed film are critical, and that the processing is temperature-dependent, resulting in variations in the gradation and the maximum density of the film. A further disadvantage is the low storage life of these images.
The second process is the classic silver halide process that yields very satisfactory images, but that is hampered by the use of a developer liquid requiring controlled regeneration in view of aerial oxidation, and the resultant inconvenience, in particular for the low-end user who makes approximately 5 to 50 microfiches per week.
It is known in other areas of photographic reproduction, for instance in graphic line and screen-work, to use light-sensitive silver halide emulsion material that incorporates its own developing agents which become active by contact with an alkaline activation solution. In this process, there is no premature oxidation of the developing agents by exposure of the developing liquid to the air as in conventional silver-halide photogrphay, whereby the processing liquid regeneration becomes simpler.
The convenience of photographic processing is further improved if the processing solutions are supplied to the different processing stations by means of holders of a reduced volume, e.g. 1 liter bottles, that are placed in inverted position on the apparatus and the contents of which is supplied to processing stations by means of a so called chicken-feed level control system.
Activation-type photographic processing apparatus of this kind can be left in stand-by condition for periods ranging from days to weeks, and yet they are capable of producing good processing results after a few seconds of running-in.
In spite of the mentioned advantages, the described inverted bottle-type processing apparatus disadvantages which make their use less convenient than is desirable.
One disadvantage is the need for a particular valve that is required for the bottles containing processing liquid, and that will be only opened at the moment the inverted bottle reaches its operative position in the apparatus.
Another disadvantage is that the holder for rinsing water must be overproportionally large, since the rinsing water becomes loaded with substances that are dissolved and leached out by the fixing of the developed photographic silver halide element. The concentration of such substances in the rinsing liquid may not exceed a given level otherwise the rinsing becomes insufficient. The latter problem may be overcome by the connection of the apparatus to a tap water supply, but this measure considerably reduces the convenience of use of the apparatus.
Finally, the different processing stations must be provided with liquid discharge means in order to empty such stations prior to their removal from the apparatus for cleaning purposes or servicing. In the case of processing sections in the form of shallow trays that are not emptied while in the apparatus, the operator must carefully remove each such tray from the apparatus and bring it to a sink for pouring away the liquid.
There is disclosed an improved photographic apparatus and method for the processing of an image-wise exposed photographic silver halide emulsion layer element in EU patent publication A1 0 271 610 entitled: "Photographic processing apparatus and method". According to this application, the holders for the different processing liquids are in the form of one common processing cassette, thereby to avoid the difficulties related with the use of different processing bottles. However the processing cassette according to this application still contains residual quantities of processing liquid when the cassette is removed by the operator from the apparatus, for instance when the useful lifetime of the cassette in the apparatus is ended, or when a pre-determined number of microfilms has been processed. In processing liquid remaining in the cassette constitute a risk for the operator or for his environment if the cassette is not handled with care.
It is the object of the present invention to provide a photographic processing cassette and an apparatus of the kind referred to, which further increase the convenience of use in operation.